Swallow-tailed Kites of the Aucilla
By Grayal Farr
On the Aucilla our mantra of priorities is: “Safety, Science, and Smell the Roses.” Part of “smelling the roses” has always been our enjoyment of the natural setting and the wildlife around our excavation sites. Of all the wildlife, the most charismatic is the Swallow-tailed Kite, Elanoides forficatus. Elegant, with white head and underparts, the bird’s back and wings are a shimmering, reflective, blue-black. This raptor is striking even in repose. Happily, we seldom see them in repose. They feed, and even drink, on the wing. And, as Peter Matthiessen writes in Wildlife in America, they “are the most graceful of hawks.” The bird guides echo that observation. Dunne, Sibley, and Sutton, in Hawks in Flight, say that “they quarter the wind flawlessly, in total aerial control” and “Time seems to have suspended for the bird.” Just as surely suspended in time, for the ARPP staff and volunteers, are the moments when the birds visit our sites. The big kites are magic - everyone feels it.
Magic or not, they are also threatened. As late as the early 1900s, the birds nested far up the major Mississippi drainages, even into Minnesota. By the 1940s their range had shrunk to that of the present. E. forficatus nests in much of peninsular Florida, and west in the panhandle to the Apalachicola River. From there west to the Sabine in Texas, and north to the Santee in South Carolina, they nest only in isolated enclaves along coastal river swamps. Matthiessen notes that they share “the tameness of all kites” and most researchers attribute their decline primarily to casual shooting.
Swallow-tailed Kites usually begin to arrive along the Aucilla in late March, about a month later than they are first seen in southwest Florida. Researchers suspect that the south Florida arrivals may have come across the Caribbean, and that our local ones have followed the Gulf coast, but little is actually known about migration routes or migratory behavior.
They nest in tall trees or snags, preferentially those in standing water, in locations with good access to open areas possessing high populations of favored prey. Wooded river swamps and pine fringes along flood plains offer these conditions, so the Aucilla is ideal habitat. Because the kites evolved to take small, easily subdued prey, they lack the grip strength or lifting capacity to manipulate sticks and large twigs. Their nests, as a result, are rather flimsy affairs. Nest collapse or blowdown is a common cause of nestling mortality.
The main cause of nestling mortality is sibling rivalry. The young birds compete, and the adults soon begin to feed the larger of their offspring preferentially. Nestlings are known to kill one another. Swallow-tailed Kites typically lay two, rarely three, eggs. They almost never fledge but one young bird.
On the river we often see them take frogs and lizards, so we tend to think of such animals as their primary prey. In fact, both adults and recently fledged young feed primarily on flying insects. They are especially adapted predators of wasps and other biting, stinging invertebrates. Kites have the thickest, most spongy stomach linings of any raptor. They have been found with stomachs full of dangerous wasps and even fire ants, the latter possibly gleaned as one of the floating masses which fire ant colonies form when their nests are flooded out. They also snatch wasp’s nests, eat the larvae, and weave the wasp’s nests into their own. The reason we so often see them with small vertebrates is that these are the foods provided to nestlings. During the May/June field season, we are observing nesting birds.
The birds are quite social. They do defend a 50-100 meter radius around nests with young, but they can often be seen hunting in groups. And especially after the year’s young fledge, they assemble in communal roosts. These communal roosting assemblages grow as the summer wanes and the birds prepare for migration. One roost in south Florida boasts over 2,000 birds. The first birds depart in late July, and by mid-September the roosts are empty. We seldom see them in the panhandle after mid-August.
During the October field seasons they are sorely missed; something vital is absent from the spirit of the river. Which makes our first sightings in spring all the more heart-lifting.
Note: Most of the science in this piece is gleaned from Ken Meyer’s excellent contribution to a compilation of life histories of North American birds. Any errors are mine, not those of Ken or any of the researchers whose work he references.
Meyer, K. D. 1995. ‘Swallow-tailed Kite (Elanoides forficatus)’. In The Birds of North America, No. 138 (A. Poole and F. Gill, eds.). The Academy of Natural Sciences, Philadelphia, and The American Ornithologist’s Union, Washington, D. C.